Flood Under Cyclone Ditwah

The Colombo Outer Circular Expressway runs largely on bridges and elevated structures, which means the main carriageway itself is not directly exposed to flooding. This elevated design provides resilience and ensures uninterrupted connectivity across the Kelani basin even during high water levels.

However, the critical vulnerability lies at the Athurugiriya entrance and the Kaduwela entrance, both of which are flood‑prone locations. When these nodes are inundated, access to the expressway is severely restricted, cutting off entry and exit points despite the elevated road remaining dry.

Secondary and minor roads dominate the dataset, with 473 segments totaling more than 101 km, while jeep/cart tracks extend over 500 km, forming the backbone of local mobility. Footpaths also stand out, with 294 segments covering 29 km, reflecting heavy pedestrian reliance in flood‑prone communities. These figures highlight that while expressways and main roads are vital for regional transport, the majority of exposure lies in community‑level routes that sustain daily access to services and evacuation points.

The land use impact assessment reveals that the region is dominated by three major categories: Built-up area, Homesteads/Gardens, and Cultivation area, with each playing a critical role in both human settlement and agricultural productivity. The Built-up area covers approximately 4,831 ha, indicating dense urban development, infrastructure, and public facilities. Within this, the subcategory of Homesteads /Gardens alone accounts for 4,706 ha, which is a clear indicator that a large portion of the population resides in these zones. These areas are highly sensitive to flood impacts, as they represent concentrated human habitation, property, and essential services. Flooding here would directly affect thousands of residents, disrupt daily life, and pose serious challenges to emergency response and recovery.

The second major focus is the Cultivation area, which spans over 5,296 ha and includes a variety of agricultural land uses. Among these, Paddy fields are the most significant, covering approximately 2,749 ha, with an additional 398 ha of abandoned paddy. Paddy cultivation is not only vital for local food security but also represents a traditional livelihood for many rural communities. Flooding in these areas can lead to crop loss, soil degradation, and long-term economic hardship for farming families. The presence of rubber, coconut, and mixed perennial crops further emphasizes the agricultural richness of the region, but paddy remains the most flood-sensitive and socially impactful land use.

In summary, the flood impact on land use must prioritize protection and resilience planning for Built-up areas and Homesteads/Gardens due to their high population density, and for Paddy lands due to their agricultural importance and vulnerability. These zones are the backbone of both urban life and rural livelihoods, and their exposure to flooding represents a dual threat to human well-being and food production. Effective mitigation strategies should focus on safeguarding these critical land use types to ensure sustainable recovery and long-term resilience.